Mechanical fasteners are widely used for joining two or more components of a structural assembly. For example, mechanical fasteners are used extensively for joining the structural components of an airframe. One-sided-installation fasteners or blind fasteners may be used in applications where access to one side of a structural assembly is unavailable. One-sided-installation fasteners may be inserted into a hole and a portion of the fastener on the blind side of the hole may be deformed. The deformed portion of the fastener on the blind side of the hole provides a bearing feature to induce preload in the fastener such that the components of the structural assembly may be clamped together.
Certain types of existing one-sided-installation fasteners may provide for a relatively large bearing area on the blind side of the hole. Unfortunately, such fasteners may either lack the ability to induce a relatively high level of preload in the fastener or such fasteners may provide for a relatively small amount of thickness variation or grip range of the clamped components. Other types of existing one-sided-installation fasteners may provide a relatively high level of fastener preload or a relatively large grip range of the clamped components. However, such fasteners may provide a small amount of bearing area which may limit the tension capability of the fastened joint.
Still other types of existing one-sided-installation fasteners may allow for a relatively large grip range of the clamped components or a relatively large amount of bearing area on the blind side of the hole. However, such fasteners may induce a relatively low level of preload in the fastener. Furthermore, the process of installing certain one-sided-installation fasteners may result in the twisting and/or inconsistent plastic deformation of the deformed portion of the fastener which may reduce the repeatability of the preload level from fastener to fastener.
Additionally, certain one-sided-installation fasteners having separate components for the head and the blind side feature may allow the deformed portion to rotate during installation which may cause damage to the structure. Furthermore, in certain one-sided-installation fasteners, the blind side formations may form in a manner allowing axial loads to produce further deformation after installation of the fastener is complete. For example, certain one-sided-installation fasteners may have an open-ended deformable portion. Excessive axial loading of the structure after the fastener is installed may result in further deformation of the deformed portion. Unfortunately, when the axial load is removed, the fastener joint may exhibit looseness in the axial direction as a result of the deformation of the open-ended deformed portion.
As can be seen, there exists a need in the art for a one-sided-installation fastener that provides for a relatively large bearing area on the blind side of the hole, a relatively high level of preload in the fastener, and a relatively large amount of thickness variation of the clamped components. In addition, there exists a need in the art for a one-sided-installation fastener with minimal or non-existent twisting of the deformed portion of the fastener during installation, and wherein the fastener is prevented from rotating relative to the structure during fastener installation, and the fastener resists additional deformation of the deformed portion after installation.